Telephone-exchange system.



Patented Jan. 23, |900.

F. n. McBERTY. TELEPHONE EXCHANGE SYSTEM.

(Application filed. Nov. 24, 1896.)

(No Model.)

NITED STATES PATENT EEICEc FRANK R. MORERTY, OE DOwNERs eROvE, ILLINOIS,AssIeNOR To THE WESTERN ELECTRIC COMPANY, OE CHICAGO, ILLINOIS.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters lliatentA No. 641,721, datedJanuary 23, 1900.

Application iiled November 24, 1896. Serial No. 613,261. (N0 model.)

To @ZZ whom t may concern:

Be it known that I, FRANK R. MCBERIY, a citizen of the United States,residing at Downers Grove, in the county of Du Page and State ofIllinois, have invented a certain new and useful Improvement inTelephone- Exchange Systems, (Case N o. 46,) of which the' following isa full, clear, concise, and exact description, reference being had tothe accompanying drawing, forming a part of this specification.

This invention applies to switching systems in which subsidiary signalsin the switchboard are controlled through the agency of a relayconnected with the line and responsive.

to currents therein determined by the position of appliances at thesubstation; and it concerns particularly the species of that systeln inwhich repeating-coils (one for each line) are employed for the purposeof rendering the signals associated with two connected linesindependently responsive to currents in the corresponding lines, therepeating-coils themselves being furnished with moving parts to serve asrelays. To describe this existing system more specifically, one windingof an induction or repeating coil is included, together with a source ofcurrent in a telephone-line, the continuity of the telephoneline beingcontrolled at the substation by the telephone-switch there. The otherwinding of the repeating-coil is included in a circuit in theswitchboard which terminates in the normally open switch-contacts ofspringjacks in the switchboard. The repeatingcoil is furnished with anarmature which controls switch-contacts in local circuits including thesubsidiary signals, one of which is permanently associated with the lineand constitutes the line-signal, the other of which is temporarilyassociated with the line through the agency of the spring-j ack andconnectingplug when connection exists with the line and. constitutes asupervisory signal for the operator. The use of repeating-coils in theline-circuit in this manner for controlling the subsidiary circuits isdemanded in some cases by certain practical considerations which arefamiliar to those versed in telephony and need not be mentioned. Theiruse in this manner is open to the objection, however, that a completedconnection between two subscribers lines involves two repeating-coilsinterposed in the circuit, whereby the efficiency of telephonictransmission is impaired.

One object of the present improvement is to so arrange the circuits ofthe lines and repeating-coils in connection with the line-jacks andanswering-jacks of the lines that no :more than one repeating-coil shallat any time be included in a telephonie circuit between two stations,although the repeating-coils of both lines remain effective foroperating signals;

A further object is to so arrange the signals that one of them shallserve to call for disconnection only, the other indicating the conditionof the substation appliances of the called line.

To this end the invention consists in leading the secondary winding ofone of the repeating-coils directly to the answering-jack of asubscribers line and in connecting the line circuit or terminals of theprimary winding of the repeating-coil with thel line-jacks of thesubscribers line, so that when two lines are united for conversation,such union being effected in the usual way by means of a plug insertedin the answering-jack of the calling-line and another plug in theline-jack of the correspondent line, the telephonie circuit involvesonly the repeating-coil associated with the calling-line. Therepeating-coils of both lines remain in connection with their respectiveline conductors, however, and both retain their functions in controllingsubsidiary signals.

The core of each repeating-coil may be furnished with a movablearmature, which may serve to control a local signal-circuit. It istherefore proper to speak of the repeatingcoil as a signal-controllingelectromagnet.

The primary and secondary windings of the repeating-coil are preferablyeach divided into two portions and each half of the primary connectedwith a corresponding half of the secondary. The two terminals of theprimary are connected with the two limbs of the telephone-line, and thetwo terminals of the secondary are connected with 'Contact portions ofthe answering-jack. The line-jack is tapped directly upon the linebetween the primary and the substation. The points of ICO junction ofthe two primary and two secondary portions ot each repeating-coil arepreferably connected together by a bridge-conductor which includes asource of current common to all the repeating-coils. Considering nowthat the answering spring-jack of one line is connected with theline-jack of another line through the usual pair of plugs andcord-circuit, we have a complete circuit made up of the united lineswith switches at the substations for controlling the continuity of thecircuit, a signal-controlling electromagnet (the repeating-coil of thecalling-line) having a winding (made up of a primary and a secondaryportion) included in series in the circuit of the united lines, abridge-circuit includinga source of current extending from a pointwithin the winding-z'. e., from thejunction of the primary and secondaryportions-to the other side of the circuit-as, for instance, to thejunction of the other two parts of the primary and secondary windings ofthe repeating-coil-and a' second signalcontrolling electromagnetassociated with the other line (in this instance the called line) havinga winding connected in a branch of the bridge-circuit from the source ofcurrent, which branch connects such winding in parallel with a portionof the windings of the first-mentioned electromagnet. The repeating-coilof the calling-line, then, is controlled by both switches-that is,current will flow through one or more of the windings of such coil ifeither switch is closed and will be deprived of current only when bothswitches are open. The repeating-coil of the called line, however, iscontrolled only by the switch at the called station, since, as isevident, the primary winding of the called line is shortcircuited, sofar as the calling-line is concerned, by the bridge-conductor whichconnects the source of current directly with the junction of the primaryand secondary wind-v ings of the repeating-coil of the calling-line.

The improvement is illustrated in the drawing herewith, wherein twosubscribers lines are represented extending to a switchboard, includingrepeating-coils in the switchboard, together with the usual switchingand signaling appliances at the central office.

Referring to the drawing, the appliances at the substation may comprisea signal-bell a, a transmitting-telephone a', a receiving-telephone a2,and a telephone-switch a3 for closing a circuit through the telephonesduring their use. The circuit through the signalbell should be of veryhigh resistance, in order that an appreciable increase in thesignalingcurrent in the line-circuit may be produced when the telephoneis brought into circuit. These appliances are connected by the lineconductors l and 2 with the apparatus in the switchboard at a centraloliice. These line conductors are connected directly with one or moreline-jacks or terminal-sockets b, several such terminal-sockets beingemployed in the case of a multiple board. The two line conductors extendfarther through two windings c and c2 of a repeating-coil c, and thenceto the terminalsof a source d of current which is common to thedifferent lines of the exchange. Two other windings c3 and c4 of therepeating-coil have two of their terminals led to the poles ot' the samebattery d and their other terminals connected by wires 3 and 4 with theswitch-contacts of an answerin g-j ack e in the switchboard. v

The repeating-coil is provided with the usual core, and a pivotedarmature c5 is arranged in position to be attracted by this core. Thisarmature is furnished with an alternatecontact c6,-with which it makescontact when attracted. This switch controls the local circuit, whichincludes the subsidiarysignals in the switchboard. =The armature-leveris connected to earth by wire 5, which includes a resistance-coil f. Thesame part is also connected by a wire 6 with the ring or thimble contactin each of the spring-jacks b and e belonging to the same line. Thecontact-anvil ci is connected by wire 7 with the free pole of a groundedsource g of current, a line signal-lamp h associated with theanswering-jack c being interposed in the wire.

The switchboard is furnished with the usual pairs of plugs t' and i',each having contactsections constructed to register with thecorresponding parts of a spring-jack into which itmaybeinserted.Thetipsandshortsleeves of the plugs are united by conductors 8 and 9,respectively, which constitute the plug-circuit and form the linkconductors which unite the lines into a telephonic circuit. The longersleeves of the plugs, which make connection with the thimbles of thespring-jacks, form the terminals of wires 10 and ll, respectively, whichlead to the free pole of battery g. In each of these wires is connecteda supervisory lamp-signal associated with the corresponding plug, thetwo signals being designated 76 and k', respectively. It will beobserved that when one of the plugs is inserted into a springjack thesupervisory lamp is brought into parallel circuit with the line-lamp h,the switch-contacts of the relay being assumed to be closed, the twobeing in series with the resistance-coil f and the battery g. Thisresistance-coil should have such resistance that the lamps under thiscondition shall not be illuminated. Then if the relay should permit itsswitch-contacts to separate the current through the resistance-coilwouldbe diverted entirely through the supervisory lamp and would cause itsillumination.

The plug-circuit is furnished with the usual appurtenances-acalling-keyl for connectingagenerator of signaling-current with plug t"and a listening-key m for connecting the operators telephone with theplug-circuit.

In the normal condition of this system no current iiows through thewindings ofthe repeating-coils, since the circuits of the lines areinterrupted at the substations. Accordingly, the relays being inert thelocal or sub- IOO IIO

sidiary signal-circuits are also interrupted, the signals therein beinginert.

The removal of the telephone from its switch at the substation permitsthe switch to close the line-circuit, whereby current is set up throughthe windings of the relay. Assume that such an act has been performed atstation A. The core of the relay being excited, the armature c5 isattracted and closes the local circuit 5 7, whereby the subsidiarysignal h is lighted. Observing this signal the operator inserts the plugz' into the answering-jack e of the line, at the same time bringing hertelephone in to connection with the plug-circuit 8 9. The act ofinserting the plug into the answering spring-jack forms the telephoniccircuitthrough conductors l 2 and 3 4 of the line, this circuit beingcompleted through the repeating-coil c. The op erator is thus enabled tocommunicate with the subscriber and learn his order. The same act hasbrought the supervisory signal lo into parallel circuit with line-signalh, whereby the latter is extinguished, the former remaining still dark.Having learned the order, the operator inserts the plug t" into a linespringjack b of the corresponding line. The plugcircuit, which forms anextension of windings c3 and o4 of repeating-coil c, is now completedirectly to the line conductors l 2 of the correspondent line. Thetelephonie circuit thus formed between the substations, it will beobserved, includes but one repeating-coil,that being coil c ofthecalling-line. The two windings c and c2 of the correspondent oranswering line remain appended to the circuit, but on account of theirimpedance do not permit the loss of telephonie current through them.lThe insertion of plug 't' in the spring-jack b of the correspondent linecompletes a circuit made up of conductors 5 and 6 of that line andstrand 11, connected with the plug. During the time between theestablishment of the connection and the response of the calledsubscriber to the operators signal the supervisory lamp k' will receiveall the current through the resistance-coil f, the conductor 7 of thecalled line being interrupted at the switch -contacts of the relay ofthat line. When, however, the called subscriber answers, removing histelephone from its switch, the core of repeating-coil c of that linebecomes excited through the action of current in its windings c and c2.That relay then closes the conductor 7, which it controls, completing ashunt about the supervisory lamp 7c', and thus bringing about itsextinction. It will be noted that if the subscriber at the callingsubstation should replace his telephone upon its switch supervisory lamplc would not become illuminated thereby, since current would still existthrough windings c3 and c4 of the same repeating-coil. When, however,both subscribers replace their telephones upon their switches, thecurrents through both repeating-coils are interrupted and both relaysinterrupt the conductors 7, which they control. Hence both supervisorylamps lo and 7c become'lighted, and thus give the signal fordisconnection. Thus the signal 7c serves only to call foradisconnection, becoming displayed only when both substationtelephoneshave been replaced. The supervisory signal k on the other hand isindependent of control by the calling-line and serves to indicate theposition of the apparat-us at the called substation at all times, andthus to signalize to the operator the reresponse of the subscribercalled.

I claim as new and desire to secure by Letters Patentl. The combinationwith two telephonelines extending from substations and adapted to beconnected together at a central ofdce to form a complete circuit, ofswitches, one at each substation, for controlling the continuity of thecircuit, a signalcontrolling electromagnet associated with one of thelines, said electromagnet having a winding c c8 included in series inthe circuit of the united lines, a bridge-circuit including a source ofcurrent, extending from a point within said winding to the other side ofthe circuit, and

a second signal-controlling electromagnet associated with the other lineand having a winding connected in a parallel branch of thebridge-circuit, whereby the first-mentioned signal-controllingelectromagnet is controlled by the switches at both substations, and theother electromagnet is controlled by the switch of one substation alone,substantially as set forth.

2. The combination with two united tele= phone-lines forming a completecircuit and switches at the substations for controlling the continuityof such circuit, of a repeatingcoil associated with one of the lines atthe central office and having two windings c 08 and c2 c4 connected onein each side of the circuit, an armature for said repeating-coilcontrolling a signal, a source of current con; nected in abridge-circuit between points Within the said windings, and a signal-controlling electromagnet associated with the other line and having awinding connected in a branch of the bridge-circuit, forming a bridgeincluding the source of current and connecting said electromagnet inparallel with one of the windings of the repeatingcoil, substantially asdescribed.

3. In combination, two telephone-lines, a repeating-coil for each linehaving its primary and its secondary windings united, a source ofcurrent and a bridge of each circuit from the point ofjnnction of thesaid windings including the source of current, a spring-jack connectedwith the primary circuit of one line, a spring-jack connected with thesecondary circuit of the other line, and plugs and a plug-circuituniting the said springjacks, an armature and switch-contacts controlledthereby for each line, and a super- IOO visory signal for each line in alocal circuit controlled by the corresponding switch-contacts,substantially as described.

4. In combination, two telephone-lines each with a switch adapted toclose the circuit at the substation during the use of the telephone, arepeating-coil for each line, the primary and secondary windings of therepeating-coil being united, a bridge of each linecircuit, and a commonsource of current in the said bridge, a line spring-jack connected withthe primary Winding of each repeatingcoil and an answering-jackconnected with the secondary Winding of each repeating-coil, plugs and aplug-circuit for uniting any answering-jack with any line-jack, anarmature and switch-contacts controlled thereby for each repeating-coil,a subsidiary line-signal for each line in a circuit controlled by thecorresponding switch-contacts, a supervisory signal for each plug, andmeans for bringing the supervisory signal into a circuit controlled bythe corresponding repeating-coil when a plug is inserted into thespring-jack of that line, substantially as described.

5. The combination with two telephonelines, of a switch at each stationfor closing the line-circuit to produce a flow of current in the lineduring the use of the telephone, an answering-jack and a line-jack foreach line, plugs for uniting any answering-jack with any line-jack, asignal-controlling instrument associated with each line, circuitconnections between the instrument and one of said spring-jacks adaptedto bring the signal-controlling magnet into circuit with both lines, andother circuit connections between the said instrument and the otherspring-jack of the line adapted to bring it into circuit with that linealone, and a bridge of the plug circuitand a source of cu rrent thereinadapted to operate the said signal-controlling instruments, asdescribed, whereby one signal is controlled by currents in both linesand the other is responsive to currentin one line only.

In witness whereof I hereunto subscribe my name this 13111 day ofAugust, A. D. 1896.

FRANK R. MCBERTY.

lVitnesses:

ELLA EDLER, LOLA J. BRINKERHOFIL

